Pyrazino[1′,2′:1,6]pyrido[3,4b]indole derivatives

ABSTRACT

Compounds of the general structural formula (I) and use of the compounds and salts and solvates thereof, as therapeutic agents.

CROSS REFERENCE TO RELATED APPLICATION

This is the U.S. national phase application of International ApplicationNo. PCT/US01/15935, filed May 15, 2001, which claims the benefit of U.S.provisional patent application Ser. No. 60/213,647, filed Jun. 23, 2000.

FIELD AND BACKGROUND OF THE INVENTION

This invention relates to a series of compounds, to methods of preparingthe compounds, to pharmaceutical compositions containing the compounds,and to their use as therapeutic agents. In particular, the inventionrelates to compounds that are potent and selective inhibitors of cyclicguanosine 3′, 5′-monophosphate specific phosphodiesterase (cGMP-specificPDE), in particular PDE5, and have utility in a variety of therapeuticareas wherein such inhibition is considered beneficial, including thetreatment of cardiovascular disorders and erectile dysfunction.

SUMMARY OF THE INVENTION

The present invention provides compounds of formula (I)

wherein R⁰, independently, is selected from the group consisting ofhalogen and C₁₋₆alkyl;

R¹ is selected from the group consisting of aryl, heteroaryl, OR^(a),SR^(a), NR^(a)R^(b), NR^(a)R^(c), NR^(a)C(═O)R^(b), NR^(a)C(═O)R^(c),C(═O)R^(a), C(═O)OR^(a), C(═O)NR^(a)R^(b), C(═O)NR^(a)R^(c),C(═O)SR^(a), C(═S)NR^(a)R^(b), C(═S)NR^(a)R^(c), SO₂R^(a),SO₂NR^(a)R^(b), SO₂NR^(a)R^(c), S(═O)R^(a), S(═O)NR^(a)R^(b),S(═O)NR^(a)R^(c), PO₃R^(a), CN, C(═O)NR^(a)C₁₋₄alkyleneOR^(a),C(═O)NR^(a)C₁₋₄alkyleneHet, C(═O)-C₁₋₄alkylenearyl,C(═O)C₁₋₄alkyleneheteroaryl, C₁₋₄-alkylenearyl substituted with one ormore of SO₂NR^(a)R^(b), NR^(a)R^(b), C(═O)OR^(a), NR^(a)SO₂CF₃, CN, NO₂,C(═O)R^(a), OR^(a), C₁₋₄alkyleneNR^(a)R^(b), andOC₁₋₄alkyleneNR^(a)R^(b), C₁₋₄alkyleneheteroaryl (with the proviso thatheteroaryl is different from thienyl, furyl, and pyridyl),C₁₋₄-alkyleneHet, C₁₋₄alkyleneC(═O)C₁₋₄alkylenearyl,C₁₋₄-alkyleneC(═O)C₁₋₄alkyleneheteroaryl, C₁₋₄alkyleneC(═O)Het,C₁₋₄alkyleneC(═O)NR^(a)R^(b), C₁₋₄alkyleneC(═O)-NR^(a)R^(c),C₁₋₄alkyleneOR^(a), C₁₋₄alkyleneNR^(a)C(═O)R^(a),C₁₋₄-alkyleneOC₁₋₄alkyleneOR^(a), C₁₋₄alkyleneNR^(a)R^(b),C₁₋₄alkyleneNR^(a)R^(c), C₁₋₄alkyleneC(═O)OR^(a), andC₁₋₄alkyleneOC₁₋₄-alkyleneC(═O)OR^(a);

R² is selected from the group consisting of an optionally substitutedmonocyclic aromatic ring selected from the group consisting of benzene,thiophene, furan, and pyridine, and an optionally substituted bicyclicring

wherein the fused ring A is a 5- or 6-membered ring, saturated orpartially or fully unsaturated, and comprises carbon atoms andoptionally one or two heteroatoms selected from oxygen, sulfur, andnitrogen;

R³ is selected from the group consisting of hydrogen and C₁₋₆alkyl;

R^(a) and R^(b), independently, are selected from the group consistingof hydrogen, C₁₋₆alkyl, C₃₋₈cycloalkyl, aryl, heteroaryl, arylC₁₋₃alkyl,heteroaryl-C₁₋₃alkyl, C₁₋₃alkylenearyl, C₁₋₃alkyleneheteroaryl, and Het;

R^(c) is phenyl or C₄₋₆cycloalkyl, either optionally substituted withone or more substituent selected from the group consisting of halo,C(═O)OR^(a), and OR^(a);

Het represents a heterocyclic group, saturated or partially unsaturated,containing at least one heteroatom selected from the group consisting ofoxygen, nitrogen, and sulfur, and optionally substituted with C₁₋₄alkylor C(═O)OR^(b);

q is 1, 2, 3, or 4; and

pharmaceutically acceptable salts and hydrates thereof.

As used herein, the term “alkyl” includes straight chained and branchedhydrocarbon groups containing the indicated number of carbon atoms,typically methyl, ethyl, and straight chain and branched propyl andbutyl groups. The hydrocarbon group can contain up to 16 carbon atoms.The term “alkyl” includes “bridged alkyl,” i.e., a C₆-C₁₆ bicyclic orpolycyclic hydrocarbon group, for example, norbornyl, adamantyl,bicyclo[2.2.2]octyl, bicyclo[2.2.1]heptyl, bicyclo[3.2.1]octyl, ordecahydronaphthyl. The term “cycloalkyl” is defined as a cyclic C₃-C₈hydrocarbon group, e.g., cyclopropyl, cyclobutyl, cyclohexyl, andcyclopentyl.

The terms “alkenyl” and “alkynyl” are defined identically as “alkyl,”except for containing a carbon-carbon double bond or carbon-carbontriple bond, respectively.

The term “alkylene” refers to an alkyl group having a substituent. Forexample, the term “C₁₋₃alkylenearyl” refers to an alkyl group containingone to three carbon atoms, and substituted with an aryl group. The term“alkenylene” as used herein is similarly defined, and contains theindicated number of carbon atoms and a carbon-carbon double bond, andincludes straight chained and branched alkenylene groups, likeethyenylene.

The term “halo” or “halogen” is defined herein to include fluorine,bromine, chlorine, and iodine.

The term “haloalkyl” is defined herein as an alkyl group substitutedwith one or more halo substituents, either fluoro, chloro, bromo, iodo,or combinations thereof. Similarly, “halocycloalkyl” is defined as acycloalkyl group having one or more halo substituents.

The term “aryl,” alone or in combination, is defined herein as amonocyclic or polycyclic aromatic group, preferably a monocyclic orbicyclic aromatic group, e.g., phenyl or naphthyl. Unless otherwiseindicated, an “aryl” group can be unsubstituted or substituted, forexample, with one or more, and in particular one to three, halo, alkyl,hydroxy, hydroxyalkyl, alkoxy, alkoxyalkyl, haloalkyl, nitro, amino,alkylamino, acylamino, alkylthio, alkylsulfinyl, and alkylsulfonyl.Examples of aryl groups include, but are not limited to, phenyl,naphthyl, tetrahydronaphthyl, 2-chlorophenyl, 3-chlorophenyl,4-chlorophenyl, 2-methylphenyl, 4-methoxyphenyl,3-trifluoromethylphenyl, 4-nitrophenyl, and the like.

The term “Het” is defined as saturated or partially unsaturatedmonocyclic, bicyclic, and tricyclic groups containing one or moreheteroatoms selected from the group consisting of oxygen, nitrogen, andsulfur. A “Het” group also can contain an oxo group (═O) attached to thering. Nonlimiting examples of Het groups include 1,3-dioxolane,2-pyrazoline, pyrazolidine, pyrrolidine, a pyrroline, 2H-pyran,4H-pyran, morpholine, thiomorpholine, piperidine, 1,4-dithiane, and1,4-dioxane.

The term “heteroaryl” is defined herein as a monocyclic or bicyclic ringsystem containing one or two aromatic rings and containing at least onenitrogen, oxygen, or sulfur atom in an aromatic ring, and which can beunsubstituted or substituted, for example, with one or more, and inparticular one to three, substituents, like halo, alkyl, hydroxy,hydroxyalkyl, alkoxy, alkoxyalkyl, haloalkyl, nitro, amino, alkylamino,acylamino, alkylthio, alkylsulfinyl, and alkylsulfonyl. Examples ofheteroaryl groups include, but are not limited to, thienyl, furyl,pyridyl, oxazolyl, quinolyl, isoquinolyl, indolyl, triazolyl,isothiazolyl, isoxazolyl, imidizolyl, benzothiazolyl, pyrazinyl,pyrimidinyl, thiazolyl, and thiadiazolyl.

The term “hydroxy” is defined as —OH.

The term “alkoxy” is defined as —OR, wherein R is alkyl.

The term “alkoxyalkyl” is defined as an alkyl group wherein a hydrogenhas been replaced by an alkoxy group. The term “(alkylthio)alkyl” isdefined similarly as alkoxyalkyl, except a sulfur atom, rather than anoxygen atom, is present.

The term “hydroxyalkyl” is defined as a hydroxy group appended to analkyl group.

The term “amino” is defined as —NH₂, and the term “alkylamino” isdefined as —NR₂, wherein at least one R is alkyl and the second R isalkyl or hydrogen.

The term “acylamino” is defined as RC(═O)N, wherein R is alkyl or aryl.

The term “alkylthio” is defined as —SR, wherein R is alkyl.

The term “alkylsulfinyl” is defined as R—SO₂, wherein R is alkyl.

The term “alkylsulfonyl” is defined as R—SO₃, wherein R is alkyl.

The term “nitro” is defined as —NO₂.

The term “trifluoromethyl” is defined as —CF₃.

The term “trifluoromethoxy” is defined as —OCF₃.

The term “cyano” is defined as —CN.

In preferred embodiments, R¹ is selected from the group consisting ofaryl, heteroaryl, OR^(a), NR^(a)R^(b), NR^(a)R^(c), C₁₋₄alkyleneHet,C₁₋₄alkyleneheteroaryl, C₁₋₄alkylenearyl,C₁₋₄alkyleneC(═O)C₁₋₄alkylenearyl, C₁₋₄alkyleneC(═O)OR^(a),C₁₋₄alkyleneC(═O)NR^(a)R^(b), C₁₋₄alkyleneC(═O)NR^(a)R^(c),C₁₋₄alkyleneC(═O)Het, C₁₋₄alkyleneNR^(a)R^(b), C₁₋₄alkyleneNR^(a)R^(c),C₁₋₄alkyleneNR^(a)C (═O)R^(a), and C₁₋₄-alkyleneOC₁₋₄ alkyleneOR^(a).

In more preferred embodiments, R¹ is selected from the group consistingof C₁₋₄alkyleneheteroaryl, wherein the heteroaryl group is selected fromthe group consisting of benzimidazole, a triazole, and imidazole;C₁₋₄alkyleneHet, wherein Het is selected from the group consisting ofpiperazine, morpholine, pyrrolidine, pyrrolidone, tetrahydrofuran,piperidine,

C₁₋₄alkyleneC₆H₅, optionally substituted with one to three groupsselected from the group consisting of C(═O)OR^(a), NR^(a)R^(b),NR^(a)SO₂CF₃, SO₂NR^(a)R^(b), CN, OR^(a), C(═O)R^(a),C₁₋₄alkyleneNR^(a)R^(b), nitro, OC₁₋₄alkylenearyl, andOC₁₋₄alkyleneNR^(a)R^(b); C₁₋₄alkyleneC(═O)benzyl;C₁₋₄alkyleneC(═O)OR^(a); C₁₋₄alkyleneC(═O)NR^(a)R^(b);C₁₋₄alkyleneC(═O)—NR^(a)R^(c); C₁₋₄alkyleneHet; NR^(a)R^(b); OH;OC₁₋₄alkyl; C₆H₅; C₁₋₄alkyleneNR^(a)R^(b); C₁₋₄alkyleneOR^(a);C₁₋₄alkyleneNHC(═O)R^(a); and C₁₋₄alkyleneOC₁₋₄alkyleneOR^(a).

In a preferred embodiment, R² is the optionally substituted bicyclicring system

wherein the bicyclic ring can represent, for example, naphthalene orindene, or a heterocycle, such as benzoxazole, benzothiazole,benzisoxazole, benzimidazole, quinoline, indole, benzothiophene, orbenzofuran, or

wherein n is an integer 1 or 2, and X, independently, are C(R^(a))₂, O,S, or NR^(a). The bicyclic ring comprising the R² substituent typicallyis attached to the rest of the molecule by a phenyl ring carbon atom.

In a preferred group of compounds of formula (I), R² is represented bymethoxyphenyl or an optionally substituted bicyclic ring

wherein n is 1 or 2, and X, independently, are CH₂ or O. Especiallypreferred R² substituents include

Within this particular group of compounds, nonlimiting examples ofsubstituents for the R² substituent include halogen (e.g., chlorine),C₁₋₃alkyl (e.g., methyl, ethyl, or i-propyl), OR^(a) (e.g., methoxy,ethoxy, or hydroxy), CO₂R^(a), halomethyl or halomethoxy (e.g.,trifluoromethyl or trifluoromethoxy), cyano, nitro, and NR^(a)R^(b).

An especially preferred subclass of compounds within the general scopeof formula (I) is represented by compounds of formula (II)

and pharmaceutically acceptable salts and solvates (e.g., hydrates)thereof.

Compounds of formula (I) can contain one or more asymmetric center, and,therefore, can exist as stereoisomers. The present invention includesboth mixtures and separate individual stereoisomers of the compounds offormula (I). Compounds of formula (I) also can exist in tautomericforms, and the invention includes both mixtures and separate individualtautomers thereof.

Pharmaceutically acceptable salts of the compounds of formula (I) can beacid addition salts formed with pharmaceutically acceptable acids.Examples of suitable salts include, but are not limited to, thehydrochloride, hydrobromide, sulfate, bisulfate, phosphate, hydrogenphosphate, acetate, benzoate, succinate, fumarate, maleate, lactate,citrate, tartrate, gluconate, methanesulfonate, benzenesulfonate, andp-toluenesulfonate salts. The compounds of the formula (I) also canprovide pharmaceutically acceptable metal salts, in particular alkalimetal salts and alkaline earth metal salts, with bases. Examples includethe sodium, potassium, magnesium, and calcium salts.

Compounds of the present invention are potent and selective inhibitorsof cGMP-specific PDE5. Thus, compounds of formula (I) are of interestfor use in therapy, specifically for the treatment of a variety ofconditions where selective inhibition of PDE5 is considered beneficial.

Phosphodiesterases (PDEs) catalyze the hydrolysis of cyclic nucleotides,such as cyclic adenosine monophosphate (cAMP) and cyclic guanosinemonophosphate (cGMP). The PDEs have been classified into at least sevenisoenzyme families and are present in many tissues (J. A. Beavo,Physiol. Rev., 75, p. 725 (1995)).

PDE5 inhibition is a particularly attractive target. A potent andselective inhibitor of PDE5 provides vasodilating, relaxing, anddiuretic effects, all of which are beneficial in the treatment ofvarious disease states. Research in this area has led to several classesof inhibitors based on the cGMP basic structure (E. Sybertz et al.,Expert. Opin. Ther. Pat., 7, p. 631 (1997)).

The biochemical, physiological, and clinical effects of PDE5 inhibitorstherefore suggest their utility in a variety of disease states in whichmodulation of smooth muscle, renal, hemostatic, inflammatory, and/orendocrine function is desirable. The compounds of formula (I),therefore, have utility in the treatment of a number of disorders,including stable, unstable, and variant (Prinzmetal) angina,hypertension, pulmonary hypertension, chronic obstructive pulmonarydisease, malignant hypertension, pheochromocytoma, congestive heartfailure, acute respiratory distress syndrome, acute and chronic renalfailure, atherosclerosis, conditions of reduced blood vessel patency(e.g., postpercutaneous transluminal coronary or carotid angioplasty, orpost-bypass surgery graft stenosis), peripheral vascular disease,vascular disorders, such as Raynaud's disease, thrombocythemia,inflammatory diseases, myocardial infarction, stroke, bronchitis,chronic asthma, allergic asthma, allergic rhinitis, glaucoma,osteoporosis, preterm labor, benign prostatic hypertrophy, peptic ulcer,preterm labor, benign prostatic hypertrophy, male erectile dysfunction,female sexual dysfunction, and diseases characterized by disorders ofgut motility (e.g., irritable bowel syndrome).

An especially important use is the treatment of male erectiledysfunction, which is one form of impotence and is a common medicalproblem. Impotence can be defined as a lack of power, in the male, tocopulate, and can involve an inability to achieve penile erection orejaculation, or both. The incidence of erectile dysfunction increaseswith age, with about 50% of men over the age of 40 suffering from somedegree of erectile dysfunction.

In addition, a further important use is the treatment of female arousaldisorder, also termed female sexual arousal disorder. Female arousaldisorders are defined as a recurrent inability to attain or maintain anadequate lubrication/swelling response of sexual excitement untilcompletion of sexual activity. The arousal response consists ofvasocongestion in the pelvis, vaginal lubrication, and expansion andswelling of external genitalia.

It is envisioned, therefore, that compounds of formula (I) are useful inthe treatment of male erectile dysfunction and female sexual arousaldisorder. Thus, the present invention concerns the use of compounds offormula (I), or a pharmaceutically acceptable salt thereof, or apharmaceutical composition containing either entity, for the manufactureof a medicament for the curative or prophylactic treatment of erectiledysfunction in a male animal and sexual arousal disorder in a femaleanimal, including humans.

The term “treatment” includes preventing, lowering, stopping, orreversing the progression or severity of the condition or symptoms beingtreated. As such, the term “treatment” includes both medical therapeuticand/or prophylactic administration, as appropriate.

It also is understood that “a compound of formula (I),” or aphysiologically acceptable salt or solvate thereof, can be administeredas the neat compound, or as a pharmaceutical composition containingeither entity.

Although the compounds of the invention are envisioned primarily for thetreatment of sexual dysfunction in humans, such as male erectiledysfunction and female sexual arousal disorder, they also can be usedfor the treatment of other disease states.

A further aspect of the present invention, therefore, is providing acompound of formula (I) for use in the treatment of stable, unstable,and variant (Prinzmetal) angina, hypertension, pulmonary hypertension,chronic obstructive pulmonary disease, malginant hypertension,pheochromocytoma, congestive heart failure, acute respiratory distresssyndrome, acute and chronic renal failure, atherosclerosis, conditionsof reduced blood vessel patency (e.g., post-PTCA or post-bypass graftstenosis), peripheral vascular disease, vascular disorders such asRaynaud's disease, thrombocythemia, inflammatory diseases, prophylaxisof myocardial infarction, prophylaxis of stroke, stroke, bronchitis,chronic asthma, allergic asthma, allergic rhinitis, glaucoma,osteoporosis, preterm labor, benign prostatic hypertrophy, male andfemale erectile dysfunction, or diseases characterized by disorders ofgut motility (e.g., IBS).

According to another aspect of the present invention, there is providedthe use of a compound of formula (I) for the manufacture of a medicamentfor the treatment of the above-noted conditions and disorders.

In a further aspect, the present invention provides a method of treatingthe above-noted conditions and disorders in a human or nonhuman animalbody which comprises administering to said body a therapeuticallyeffective amount of a compound of formula (I).

Compounds of the invention can be administered by any suitable route,for example by oral, buccal, inhalation, sublingual, rectal, vaginal,transurethral, nasal, topical, percutaneous, i.e., transdermal, orparenteral (including intravenous, intramuscular, subcutaneous, andintracoronary) administration. Parenteral administration can beaccomplished using a needle and syringe, or using a high pressuretechnique, like POWDERJECT™.

Oral administration of a compound of the invention is the preferredroute. Oral administration is the most convenient and avoids thedisadvantages associated with other routes of administration. Forpatients suffering from a swallowing disorder or from impairment of drugabsorption after oral administration, the drug can be administeredparenterally, e.g., sublingually or buccally.

Compounds and pharmaceutical compositions suitable for use in thepresent invention include those wherein the active ingredient isadministered in an effective amount to achieve its intended purpose.More specifically, a “therapeutically effective amount” means an amounteffective to prevent development of, or to alleviate the existingsymptoms of, the subject being treated. Determination of the effectiveamounts is well within the capability of those skilled in the art,especially in light of the detailed disclosure provided herein.

A “therapeutically effective dose” refers to that amount of the compoundthat results in achieving the desired effect. Toxicity and therapeuticefficacy of such compounds can be determined by standard pharmaceuticalprocedures in cell cultures or experimental animals, e.g., fordetermining the LD₅₀ (the dose lethal to 50% of the population) and theED₅₀ (the dose therapeutically effective in 50% of the population). Thedose ratio between toxic and therapeutic effects is the therapeuticindex, which is expressed as the ratio between LD₅₀ and ED₅₀. Compoundswhich exhibit high therapeutic indices are preferred. The data obtainedfrom such data can be used in formulating a range of dosage for use inhumans. The dosage of such compounds preferably lies within a range ofcirculating concentrations that include the ED₅₀ with little or notoxicity. The dosage can vary within this range depending upon thedosage form employed, and the route of administration utilized.

The exact formulation, route of administration, and dosage can be chosenby the individual physician in view of the patient's condition. Dosageamount and interval can be adjusted individually to provide plasmalevels of the active moiety which are sufficient to maintain thetherapeutic effects.

The amount of composition administered is dependent on the subject beingtreated, on the subject's weight, the severity of the affliction, themanner of administration, and the judgment of the prescribing physician.

Specifically, for administration to a human in the curative orprophylactic treatment of the conditions and disorders identified above,oral dosages of a compound of formula (I) generally are about 0.5 toabout 1000 mg daily for an average adult patient (70 kg). Thus, for atypical adult patient, individual tablets or capsules contain 0.2 to 500mg of active compound, in a suitable pharmaceutically acceptable vehicleor carrier, for administration in single or multiple doses, once orseveral times per day. Dosages for intravenous, buccal, or sublingualadministration typically are 0.1 to 500 mg per single dose as required.In practice, the physician determines the actual dosing regimen which ismost suitable for an individual patient, and the dosage varies with theage, weight, and response of the particular patient. The above dosagesare exemplary of the average case, but there can be individual instancesin which higher or lower dosages are merited, and such are within thescope of this invention.

For human use, a compound of the formula (I) can be administered alone,but generally is administered in admixture with a pharmaceutical carrierselected with regard to the intended route of administration andstandard pharmaceutical practice. Pharmaceutical compositions for use inaccordance with the present invention thus can be formulated in aconventional manner using one or more physiologically acceptablecarriers comprising excipients and auxiliaries that facilitateprocessing of compounds of formula (I) into preparations which can beused pharmaceutically.

These pharmaceutical compositions can be manufactured in a conventionalmanner, e.g., by conventional mixing, dissolving, granulating,dragee-making, levigating, emulsifying, encapsulating, entrapping, orlyophilizing processes. Proper formulation is dependent upon the routeof administration chosen. When a therapeutically effective amount of acompound of the present invention is administered orally, thecomposition typically is in the form of a tablet, capsule, powder,solution, or elixir. When administered in tablet form, the compositioncan additionally contain a solid carrier, such as a gelatin or anadjuvant. The tablet, capsule, and powder contain about 5% to about 95%compound of the present invention, and preferably from about 25% toabout 90% compound of the present invention. When administered in liquidform, a liquid carrier such as water, petroleum, or oils of animal orplant origin can be added. The liquid form of the composition canfurther contain physiological saline solution, dextrose or othersaccharide solutions, or glycols. When administered in liquid form, thecomposition contains about 0.5% to about 90% by weight of a compound ofthe present invention, and preferably about 1% to about 50% of acompound of the present invention.

When a therapeutically effective amount of a compound of the presentinvention is administered by intravenous, cutaneous, or subcutaneousinjection, the composition is in the form of a pyrogen-free,parenterally acceptable aqueous solution. The preparation of suchparenterally acceptable solutions, having due regard to pH, isotonicity,stability, and the like, is within the skill in the art. A preferredcomposition for intravenous, cutaneous, or subcutaneous injectiontypically contains, in addition to a compound of the present invention,an isotonic vehicle.

For oral administration, the compounds can be formulated readily bycombining a compound of formula (I) with pharmaceutically acceptablecarriers well known in the art. Such carriers enable the presentcompounds to be formulated as tablets, pills, dragees, capsules,liquids, gels, syrups, slurries, suspensions and the like, for oralingestion by a patient to be treated. Pharmaceutical preparations fororal use can be obtained by adding a compound of formula (I) with asolid excipient, optionally grinding a resulting mixture, and processingthe mixture of granules, after adding suitable auxiliaries, if desired,to obtain tablets or dragee cores. Suitable excipients include, forexample, fillers and cellulose preparations. If desired, disintegratingagents can be added.

For administration by inhalation, compounds of the present invention areconveniently delivered in the form of an aerosol spray presentation frompressurized packs or a nebulizer, with the use of a suitable propellant.In the case of a pressurized aerosol, the dosage unit can be determinedby providing a valve to deliver a metered amount. Capsules andcartridges of, e.g., gelatin, for use in an inhaler or insufflator canbe formulated containing a powder mix of the compound and a suitablepowder base such as lactose or starch.

The compounds can be formulated for parenteral administration byinjection, e.g., by bolus injection or continuous infusion. Formulationsfor injection can be presented in unit dosage form, e.g., in ampules orin multidose containers, with an added preservative. The compositionscan take such forms as suspensions, solutions, or emulsions in oily oraqueous vehicles, and can contain formulatory agents such as suspending,stabilizing, and/or dispersing agents.

Pharmaceutical formulations for parenteral administration includeaqueous solutions of the active compounds in water-soluble form.Additionally, suspensions of the active compounds can be prepared asappropriate oily injection suspensions. Suitable lipophilic solvents orvehicles include fatty oils or synthetic fatty acid esters. Aqueousinjection suspensions can contain substances which increase theviscosity of the suspension. Optionally, the suspension also can containsuitable stabilizers or agents that increase the solubility of thecompounds and allow for the preparation of highly concentratedsolutions. Alternatively, a present composition can be in powder formfor constitution with a suitable vehicle, e.g., sterile pyrogen-freewater, before use.

Compounds of the present invention also can be formulated in rectalcompositions, such as suppositories or retention enemas, e.g.,containing conventional suppository bases. In addition to theformulations described previously, the compounds also can be formulatedas a depot preparation. Such long-acting formulations can beadministered by implantation (for example, subcutaneously orintramuscularly) or by intramuscular injection. Thus, for example, thecompounds can be formulated with suitable polymeric or hydrophobicmaterials (for example, as an emulsion in an acceptable oil) or ionexchange resins, or as sparingly soluble derivatives, for example, as asparingly soluble salt.

Many of the compounds of the present invention can be provided as saltswith pharmaceutically compatible counterions. Such pharmaceuticallyacceptable base addition salts are those salts that retain thebiological effectiveness and properties of the free acids, and that areobtained by reaction with suitable inorganic or organic bases.

In particular, a compound of formula (I) can be administered orally,buccally, or sublingually in the form of tablets containing excipients,such as starch or lactose, or in capsules or ovules, either alone or inadmixture with excipients, or in the form of elixirs or suspensionscontaining flavoring or coloring agents. Such liquid preparations can beprepared with pharmaceutically acceptable additives, such as suspendingagents. A compound also can be injected parenterally, for example,intravenously, intramuscularly, subcutaneously, or intracoronarily. Forparenteral administration, the compound preferably is used in the formof a sterile aqueous solution which can contain other substances, forexample, salts, or monosaccharides, such as mannitol or glucose, to makethe solution isotonic with blood.

For veterinary use, a compound of formula (I) or a nontoxic saltthereof, is administered as a suitably acceptable formulation inaccordance with normal veterinary practice. The veterinarian can readilydetermine the dosing regimen and route of administration that is mostappropriate for a particular animal.

Thus, the invention provides in a further aspect a pharmaceuticalcomposition comprising a compound of the formula (I), together with apharmaceutically acceptable diluent or carrier therefor. There isfurther provided by the present invention a process of preparing apharmaceutical composition comprising a compound of formula (I), whichprocess comprises mixing a compound of formula (I), together with apharmaceutically acceptable diluent or carrier therefor.

In a particular embodiment, the invention includes a pharmaceuticalcomposition for the curative or prophylactic treatment of erectiledysfunction in a male animal, or sexual arousal disorder in a femaleanimal, including humans, comprising a compound of formula (I) or apharmaceutically acceptable salt thereof, together with apharmaceutically acceptable diluent or carrier.

Compounds of formula (I) can be prepared by any suitable method known inthe art, or by the following processes which form part of the presentinvention. In the methods below, R⁰, R¹, R², and R³, are defined as instructural formula (I) above. In particular, Daugan U.S. Pat. No.5,859,006, incorporated herein by reference, discloses preparation of acompound of structural formula (III)

wherein R⁴ is selected from the group consisting of hydrogen, C₁₋₆alkyl,C₂₋₆alkenyl, C₂₋₆alkynyl, haloC₁₋₆alkyl, C₃₋₈cycloalkyl,C₃₋₈cycloalkylC₁₋₃alkyl, arylC₁₋₃alkyl, and heteroarylC₁₋₃alkyl.

Daugan U.S. Pat. No. 5,859,006 teaches the preparation of the compoundof structural formula (III) from a compound having the structuralformula (IV):

The compounds of structural formula (I) can be prepared in an analogousmanner as a compound of structural formula (III) using an appropriatelyR⁰ and R² substituted compound of structural formula (IV) by thefollowing exemplary synthetic sequence wherein R² is

Compound VI is synthesized by cyclization of the known chloro-compound(V) with a substituted amine in a suitable solvent to provide thediketopiperazine compound (VI).

Imide and N-acyl sulfonamide compounds are synthesized by treatment ofan amide (VII), disclosed in U.S. Pat. No. 5,859,006 as Example 4, withan appropriately substituted acyl chloride (VII→VIII) or sulfonylchloride (VII→IX) in methylene chloride and triethylamine catalyst:

Many substituted acyl chlorides and substituted sulfuryl chlorides arecommercially available, and, if necessary, can be converted to othersubstituents after formation of compound (VIII) or (IX).

It should be understood that protecting groups can be utilized inaccordance with general principles of organic synthetic chemistry toprovide compounds of structural formula (I). Protecting compounds andprotecting groups, like benzyl chloroformate and trichloroethylchloroformate, are well known to persons skilled in the art, forexample, see T. W. Greene et al., “Protective Groups in OrganicSynthesis, Third Edition,” John Wiley and Sons, Inc., NY, N.Y. (1999).These protecting groups are removed when necessary by appropriate basic,acidic, or hydrogenolytic conditions known to persons skilled in theart. Accordingly, compounds of structural formula (I) not specificallyexemplified herein can be prepared by persons skilled in the art.

In addition, compounds of formula (I) can be converted to othercompounds of formula (I). Thus, for example, a particular R¹ substituentcan be interconverted to prepare another suitably substituted compoundof formula (I). Examples of appropriate interconversions include, butare not limited to, OR^(a) to hydroxy by suitable means (e.g., using anagent such as SnCl₂ or a palladium catalyst, like palladium-on-carbon),or amino to substituted amino, such as acylamino or sulphonylamino,using standard acylating or sulfonylating conditions.

Compounds of formula (I) can be prepared by the method above asindividual stereoisomers from the appropriate stereoisomer of formula(IV) or as a racemic mixture from the appropriate racemic compound offormula (IV). Individual stereoisomers of the compounds of the inventioncan be prepared from racemates by resolution using methods known in theart for the separation of racemic mixtures into their constituentstereoisomers, for example, using HPLC on a chiral column, such asHypersil naphthyl urea, or using separation of salts of stereoisomers.Compounds of the invention can be isolated in association with solventmolecules by crystallization from, or evaporation of, an appropriatesolvent.

The pharmaceutically acceptable acid addition salts of the compounds offormula (I) that contain a basic center can be prepared in aconventional manner. For example, a solution of the free base can betreated with a suitable acid, either neat or in a suitable solution, andthe resulting salt isolated either by filtration or by evaporation undervacuum of the reaction solvent. Pharmaceutically acceptable baseaddition salts can be obtained in an analogous manner by treating asolution of a compound of formula (I) with a suitable base. Both typesof salt can be formed or interconverted using ion-exchange resintechniques. Thus, according to a further aspect of the invention, amethod for preparing a compound of formula (I) or a salt or solvate(e.g., hydrate) is provided, followed by (i) salt formation, or (ii)solvate (e.g., hydrate) formation.

The following additional abbreviations are used hereafter in theaccompanying examples: rt (room temperature), min (minute), h (hour), g(gram), mmol (millimole), m.p. (melting point), eq (equivalents), L(liter), mL (milliliter), μL (microliter), DMSO (dimethyl sulfoxide),CH₂Cl₂ (dichloromethane), IPA (isopropyl alcohol), TFA (trifluoroaceticacid), TEA (triethylamine), EtOH (ethanol), MeOH (methanol), DMF(dimethylformamide), Et₃N (triethylamine), MeNH₂ (methylamine), AcOH(acetic acid), and THF (tetrahydrofuran).

PREPARATION OF EXAMPLE 1

EXAMPLE 1

Example 1, and all other examples, were prepared using the followinggeneral method. All nonaqueous reactions were performed under a drynitrogen atmosphere. Reagents and anhydrous solvents were purchased fromcommercial sources and used as received, unless otherwise noted. Meltingpoints were obtained by differential scanning colorimetry (DSC) using aPerkin Elmer Model DSC-4 unit, or were obtained using an Electrothermalunit, and are uncorrected. Thin layer chromatography was performed using1 inch×3 inch Analtech GF 350 silica gel plates with a fluorescentindicator. TLC plates were observed under a UV lamp, in iodine vapors,or by dipping in commercial phosphomolybdic acid solution, followed bywarming. Infrared (1R) spectra were obtained on a single-beamPerkin-Elmer Spectrum 1000 FT-IR spectrometer using 4 accumulations at aresolution of 4.00 cm⁻¹ on samples prepared in a pressed disc ofpotassium bromide (KBr) or as a film on sodium chloride (NaCl) plates.Proton NMR spectra (300 MHz, referenced to tetramethylsilane) and carbonNMR spectra. (75 MHz, proton decoupled, referenced to residual solvent,signals) were obtained on a Bruker AC 300 spectrometer. Proton NMRspectra (500 MHz, referenced to tetramethylsilane) were obtained on aBruker AMX 500 spectrometer. Mass spectra were obtained on a ShimadzuQP-5000 GC/MS mass spectrometer (CI mass spectrometry). Chiral HPLCanalyses were obtained using a Chiracel OD column (250×4.6 mm) atambient temperature with UV detection at 222 nm using an isochraticsolvent system (1:1 isopropanol hexanes). Elemental analyses wereperformed by Quantitative Technologies, Inc., Whitehouse, N.J.

Example 1 was prepared from compound (V) (R⁰═H, see Intermediate 2 inExample 2) by the following reaction:

EXAMPLE 1 Preparation of(6R-trans)-6-(1,3-Benzodioxol-5-yl)-2,3,6,7,12,12a-hexahydro-2-[2-(4-phenylsulfamoyl)-ethyl]pyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione

A mixture of Compound (V) (4.27 g, 10.0 mmol) and4-(2-aminoethyl)benzenesulfonamide (4.0 g, 20 mmol) in methanol (50 mL)and THF (25 mL) was heated at 45° C. for 22 hours. The resulting clearsolution was concentrated to dryness, and the residue was stirred inmethanol (40 mL) for 20 minutes. The resulting white solid was collectedby vacuum filtration, and washed with methanol (5×20 mL), followed byhexanes (3×20 mL), then dried in a vacuum oven at 40° C. to yieldExample 1 as a white powder (5.0 g, 89.5%): TLC R_(f) (3:1 methylenechloride/ethyl acetate)=0.11; ¹H NMR (300 MHz, DMSO-d₆): δ 11.08 (s,1H), 7.75 (d, J=8.2 Hz, 2H), 7.54 (d, J=7.6 Hz, 1H), 7.43 (d, J=8.2 Hz,2H), 7.31 (d, J=7.6 Hz, 1H), 7.30-6.91 (m, 4H), 6.89 (s, 1H), 6.85-6.70(m, 2H), 6.16 (s, 1H), 5.94 (s, 2H), 4.41 (dd, J=11.5, 4.7 Hz, 1H), 4.17(d, J=16.9 Hz, 1H), 3.97 (d, J=16.9 Hz, 1H), 3.73-3.50 (m, 2H), 3.48(dd, J=15.8, 4.4 Hz, 1H), 3.05-2.81 (m, 3H); ¹³C NMR (125 MHz, DMSO-d₆):δ 167.1, 165.6, 147.1, 146.1, 143.0, 142.2, 137.0, 136.2, 133.9, 129.3,125.8, 121.3, 119.0, 118.1, 111.3, 108.1, 106.9, 104.6, 101.0, 55.4,55.1, 50.0, 48.5, 32.4, 22.1 ppm; API MS m/z 559 (C₂₉H₂₆N₄O₆S+H)⁺;[α]_(D) ^(27° C.)=+41.6° (c=1.0, DMSO). Anal. Calcd. for C₂₉H₂₆N₄O₆S: C,62.35; H, 4.69; N, 10.03; S, 5.74. Found: C, 61.99; H, 4.76; N, 10.11;S, 5.81. The stereochemistry of Example 1 was confirmed to be thedesired cis isomer by an NOE difference experiment (DMSO-d₆): positiveNOE enhancements from the C12a proton at 4.41 ppm to the C6 proton at6.16 ppm (0.5%) and a C12 proton at 3.48 ppm (3.4%).

PREPARATION OF EXAMPLE 2

Example 2 was prepared from a starting tryptophan ester hydrochloridewhich is commercial available from Aldrich Chemical Co., Milwaukee, Wis.The reaction sequence is disclosed in Daugan U.S. Pat. No. 5,859,006,incorporated herein by reference. The reaction sequence include thesteps of

EXAMPLE 2

Preparation of Intermediate 1

(1R,3R)-1-Benzo[1,3]dioxol-5-yl-2,3,4,9-tetrahydro-1H-β-carboline-3-carboxylicAcid Methyl Ester Hydrochloride

D-Tryptophan methyl ester hydrochloride (50.0 g, 0.196 mol, 0.5 eq) wassuspended in 500 ml acetic acid, water (10 ml), then piperonal (88.0 g,0.586 mol, 1.5 31) was added. The resulting mixture was stirred at 50°C. for 24 hours. A second charge of 50.0 g D-tryptophan methyl esterhydrochloride then was added to the clear solution. After 73 hours, theresulting suspension was cooled to ambient temperature and diluted with1.2 L ethyl acetate followed by 300 ml methyl t-butyl ether. The mixturethen was cooled in an ice bath, the solid collected by filtration,rinsed with 2×100 ml methyl t-butyl ether, and dried in vacuo to yield90.2 g (59% yield) of Intermediate 1 as a white solid: mp 215-216° C.;¹H NMR (DMSO-d₆): δ 10.85 (s, 1H), 10.55 (br s, 1H), 10.12 (br s, 1H),7.54 (d, J=7.6, 1H), 7.29 (d, J=7.9, 1H), 7.14-7.01 (m, 4H), 6.97 (s,1H), 6.10 (s, 2H), 5.86 (br s, 1H), 4.76 (m, 1H), 3.85 (s, 3H), 3.37 (dof d, J₁=15.9, J₂=4.8, 1H), 3.24 (t, J=13.6, 1H); MS m/z 351 (M+H);[α]_(D) ^(21° C.)=54.8 (c=0.5, DMSO); Anal. Calcd. for C₂₀H₁₈N₂O₄HCl: C,62.10; H, 4.95; N, 7.24. Found: C, 61.33; H, 4.98; N, 7.03.

Preparation of Intermediate 2

(1R,3R)-1-Benzo[1,3]dioxol-5-yl-2-(2-chloroethanoyl)2,3,4,9-tetrahydro-1H-β-carboline-3-carboxylicAcid Methyl Ester

Intermediate 1 (60.0 g, 0.155 mol) was suspended in 60 ml acetone.Triethylamine (36.0 g, 0.356 mol, 2.3 eq) then was added to thesuspension. The resulting mixture was cooled to 0° C. in an ice bath,then chloroacetyl chloride (22.8 g, 0.202 mol, 1.3 eq) was added over 2hours with stirring. The mixture was stirred at ambient temperature foran additional 1.5 hours, then 1.2 L water was added to slowlyprecipitate a solid. The mixture was cooled to 0° C. and held for 1hour. The solid then was collected by vacuum filtration and washed withwater. The solid was triturated with isopropyl alcohol, collected byfiltration, and washed with portions of IPA. The resulting pale yellowsolid (Intermediate 2) was dried in vacuo to yield 58.1 g (88% yield):mp 207-208° C.; ¹H NMR (DMSO-d₆): δ 10.89 (s, 1H), 7.55 (d, J=7.6, 1H),7.29 (d, J=7.9, 1H), 7.10 (t, J=7.1, 1H), 7.03 (t, J=7.1, 1H), 6.81 (d,J=8.1, 1H), 6.76 (s, 1H), 6.64 (s, 1H), 6.45 (d, J=7.1, 1H), 5.98 (d,J=6.1, 2H), 5.20 (d, J=6.5, 1H), 4.85 (d, J=13.9, 1H), 4.45 (d, J=13.9,1H), 3.47 (d, J=15.9, 1H), 3.08 (d of d, J₁=16.3, J₂=7.0, 1H), 3.04 (s,3H); MS m/z 427 (M+H); [α]_(D) ^(23° C.)=−120.9 (c=0.5, DMSO); Anal.Calcd. for C₂₂H₁₉N₂O₅Cl: C, 61.43; H, 4.49; N, 6.56. Found: C, 61.82; H,4.45; N, 6.55.

PREPARATION OF EXAMPLE 2

(6R,12aR)-6-Benzo[1,3]dioxo-5-yl-2-hydroxy-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]-pyrido[3,4-b]indole-1,4-dione

Intermediate 2 (3.45 g, 8.08 mmol) and hydroxylamine hydrochloride (1.12g, 16.2 mmol) were suspended in tetrahydrofuran. While stirring, 3.5 mlwater and then 2.82 ml (16.2 mmol) diisopropylethylamine were added tothe mixture. The resulting mixture was heated at 45° C. in an oil bathfor 24 hours. The reaction mixture was allowed to cool to roomtemperature, then was poured into-ethyl acetate, washed with saturatedNaCl, dried over sodium sulfate (Na₂SO₄), filtered, and the solventstripped on a rotary evaporator. The resulting residue wasrecrystallized from ethyl acetate to yield 2.09 g (66%) of Example 2 asan off-white solid: mp=276-283° C. (dec.); ¹H NMR (DMSO-d₆): δ 10.99 (s,1H), 10.23 (s, 1H), 7.55 (d, J=7.4, 1H), 7.29 (d, J=7.8, 1H), 7.06 (t,J=7.3, 1H), 6.99 (t, J=7.5, 1H), 6.88 (s, 1H), 6.84-6.77 (m, 2H), 6.05(s, 1H), 5.93 (d, J=2.3, 2H), 4.45 (d of d, J₁=12.1, J₂=4.0, 1H), 4.39(d, J=19.9, 1H), 4.10 (d, J=16.4, 1H), 3.57 (d of d, J₁=15.3, J₂=11.9,1H); MS m/z 332 (M+H), 414 (M+Na); [α]_(D) ^(27° C.)=106.6 (c=0.05,DMSO); Anal. Calcd. for C₂₁H₁₇N₃O₅; C, 64.45; H, 4.38; N, 10.74. Found:C, 64.14; H, 4.55; N, 10.55. Stereochemistry was confirmed by NOEexperiments: Positive NOE enhancements observed from C12a (4.39 ppm) toC6 (6.05 ppm) and from C6 to C12a.

PREPARATION OF EXAMPLE 3(6R,12aR)-6-Benzo[1,3]dioxol-5-yl-2-methoxy-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]-pyrido[3,4-b]indole-1,4-dione

Example 3 was prepared directly from Example 2 as follows:

Example 2 (0.278 g, 0.710 mmol) was added to a dried flask andmaintained under a nitrogen atmosphere. Example 2 was suspended inanhydrous dimethylformamide, then dry K₂CO₃ (0.247 g, 1.79 mmol) wasadded followed by 0.049 ml (0.78 mmol) methyl iodide. The resultingmixture was stirred magnetically under a nitrogen blanket for 24 hours.The reaction then was diluted with ethyl acetate and washed withsaturated sodium bicarbonate (NaHCO₃), 1N hydrochloric acid (HCl), andsaturated NaCl, dried over Na₂SO₄, filtered and the solvent stripped ona rotary evaporator. The resulting residue was purified by flashchromatography (CH₂Cl₂/ethyl acetate/methanol (90:10:1) followed byrecrystallization (methanol) to yield, after drying, 79 mg (27% yield)of Example 3 as a white crystalline solid: mp=268-270° C.; TLC R_(f)(CH₂Cl₂/ethyl acetate/methanol)=0.24; ¹H NMR (DMSO-d₆): δ 10.95 (s, 1H),7.54 (d, J=7.3, 1H), 7.28 (d, J=7.7, 1H), 7.05 (t, J=7.6; 1H), 6.99 (t,J=7.6, 1H), 6.88 (s, 1H), 6.84-6.77 (m, 2H), 6.03 (s, 1H), 5.92 (d,J=3.9, 2H), 4.43 (d of d, J₁=11.7, J₂=3.8, 1H), 4.40 (d, J=14.6, 1H),4.31 (d, J=16.1, 1H), 3.76 (s, 3H), 3.55 (d of d, J₁=15.7, J₂=4.1, 1H),3.02 (d of d, J₁=15.0, J₂=11.8, 1H); MS m/z 406 (M+H), 428 (M+Na);[α]_(D) ^(25° C.=)91.7 (c=0.1, DMSO); Anal. Calcd. for C₂₂H₁₉N₃O₅: C,65.18; H, 4.72; N, 10.36. Found: C, 64.87; H, 4.60; N, 10.27.Stereochemistry was confirmed by NOE experiments: Positive NOEenhancements observed from C12a (4.43 ppm) to C6 (6.03 ppm) and from C6to C12a.

PREPARATION OF EXAMPLE 4(6R,12aR)-2-Amino-6-benzo[1,3]dioxo-5-yl-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]-pyrido[3,4-b]indole-1,4-dione

Example 4 was prepared in one step from Intermediate 2 as follows:

EXAMPLE 4

A mixture of Intermediate 2 (2.14 g, 5 mmol) and hydrazine hydrate (1.2mL, 25 mmol) in methanol (20 mL) was stirred at room temperature under anitrogen blanket for 2 days. To aid solubility, THF (7 mL) was added tothe mixture, and the resulting mixture was stirred at room temperaturefor an additional 2.5 days. The white solid was collected by vacuumfiltration, washed with methanol (10×5 mL), then dried in a vacuum ovenat 60° C. for 2 days to yield Example 4 as a white powder (1.6 g, 82%),which was confirmed to be the desired cis isomer by NOE analysis (2.4%enhancement): mp 272-278° C.; TLC R_(f) (4:1:0.5 methylenechloride/ethyl acetate/methanol)=0.49; ¹H NMR (300 MHz, DMSO-d₆): δ11.01 (s, 1H), 7.55 (d, J=7.5 Hz, 1H), 7.30 (d, J=7.5 Hz, 1H), 7.09-6.98(m, 2H), 6.89-6.76 (m, 3H), 6.11 (s, 1H), 5.93 (s, 2H), 5.12 (s, 2H),4.47-4.42 (m, 1H), 4.27 (d, J=17.0 Hz, 1H), 3.97 (d, J=17.0 Hz, 1H),3.61-3.55 (m, 1H), 3.04-2.95 (m, 1H); ¹³C NMR (75 MHz, DMSO-d₆): δ166.2, 164.6, 147.0, 146.0, 137.0, 136.2, 133.9, 125.7, 121.2, 119.3,118.8, 118.0, 111.2, 107.9, 106.9, 104.8, 100.8, 55.5, 55.3, 53.3, 23.3ppm; CI MS (methane) m/z 391 [M+H]⁺; [α]_(D) ^(25° C.)=+75.7 (c=1.0,DMSO). Anal. Calcd. for C₂₁H₂₀N₄O₃; C, 64.61; H, 4.65; N, 14.35. Found:C, 64.41; H, 4.56; N, 14.31.

The following Examples 5 and 7-88 were prepared by methods analogous toExamples 1-4.

Exam- ple R¹ R² ¹⁾ R³ 1

1 H 2 —OH 1 H 3 —OCH₃ 1 H 4 —NH₂ 1 H 5 —NHCH₃ 1 H 7

1 H 8 —CH₂CH₂N(CH₃)₂ 1 CH₃ 9 —CH₂CH₂N(CH₃)₂ 2 H 10 —CH₂CH₂OH 1 H 11—(CH₂)₃N(CH₃)₂ 2 H 12

2 H 13

1 H 14

1 H 15

1 H 16

1 H 17

2 H 18

1 H 19 —CH₂C(═O)OCH₃ 1 H 20 —CH₂C(═O)NH₂ 1 H 21

1 H 22

1 H 23

1 H 24 —(CH₂)₂C(═O)OCH₂CH₃ 1 H 25 —(CH₂)₃OCH₃ 1 H 26 —(CH₂)₂NHC(═O)CH₃ 1H 27

1 H 28 —CH₂C(═O)NH—C₆H₅ 1 H 29 —(CH₂)₂OCH₃ 1 H 30 —CH₂C(═O)NHCH₂—C₆H₅ 1H 31

1 H 32

1 H 33

1 H 34

1 H 35

1 H 36 —(CH₂)₂C(═O)OH 1 H 37

1 H 38

1 H 39 —(CH₂)₃OCH₂CH₃ 1 H 40 —(CH₂)₂O(CH₂)₂OH 1 H 41

1 H 42

1 H 43

1 H 44

1 H 45

1 H 46

1 H 47

1 H 48

1 H 49

1 CH₃ 50

1 H 51

1 H 52

2 H 53

1 H 54

1 H 55

1 H 56

1 H 57

1 H 58

1 H 59

1 H 60 —CH₂CN 1 H 61

1 H 62

1 H 63

1 H 64

1 H 65

1 H 66

1 H 67

1 H 68 —CH₂C(═O)OCH₂C₆H₅ 1 H 69 —CH₂C(═O)OH) 1 H 70

1 H 71 —(CH₂)₂C(═O)OC(CH₃)₃ 1 H 72 —(CH₂)₂C(═O)OH 1 H 73

1 H 74

1 H 75

1 H 76

1 H 77

1 H 78

1 H 79

1 H 80

1 H 81

1 H 82

1 H 83

1 H 84

1 H 85

1 H 86 —CH₂C(═O)OC(CH₃)₃ 1 H 87 —CH₂C(═O)OCH₃ 1 H 88 —CH₂C(═O)O(CH₂)₇CH₃1 H ¹⁾for R², the designation 1 is

and the designation 2 is

Compounds of the present invention can be formulated into tablets fororal administration. For example, a compound of formula (I) can beformed into a dispersion with a polymeric carrier by the coprecipitationmethod set forth in WO 96/38131, incorporated herein by reference. Thecoprecipitated dispersion then can be blended with excipients, thenpressed into tablets, which optionally are film-coated.

The compounds of structural formula (I) were tested for an ability toinhibit PDE5. The ability of a compound to inhibit PDE5 activity isrelated to the IC₅₀ value for the compound, i.e., the concentration ofinhibitor required for 50% inhibition of enzyme activity. The IC₅₀ valuefor compounds of structural formula (I) were determined usingrecombinant human PDE5.

The compounds of the present invention typically exhibit an IC₅₀ valueagainst recombinant human PDE5 of less than about 50 μM, and preferablyless than about 25 μM, and more preferably less than about 15 μm. Thecompounds of the present invention typically exhibit an IC₅₀ valueagainst recombinant human-PDE5 of less than about 1 μM, and often lessthan about 0.05 μM. To achieve the full advantage of the presentinvention, a present PDE5 inhibitor has an IC₅₀ of about 0.1 nM to about15 μM.

The production of recombinant human PDEs and the IC₅₀ determinations canbe accomplished by well-known methods in the art. Exemplary methods aredescribed as follows:

Expression of Human PDEs

Expression in Saccharomyces cerevisiae (Yeast)

Recombinant production of human PDE1B, PDE2, PDE4A, PDE4B, PDE4C, PDE4D,PDE5, and PDE7 was carried out similarly to that described in Example 7of U.S. Pat. No. 5,702,936, incorporated herein by reference, exceptthat the yeast transformation vector employed, which is derived from thebasic ADH2 plasmid described in Price et al., Methods in Enzymology,185, pp. 308-318 (1990), incorporated yeast ADH2 promoter and terminatorsequences and the Saccharomyces cerevisiae host was theprotease-deficient strain BJ2-54 deposited on Aug. 31, 1998 with theAmerican Type Culture Collection, Manassas, Va., under accession numberATCC 74465. Transformed host cells were grown in 2×SC-leu medium, pH6.2, with trace metals, and vitamins. After 24 hours, YEPmedium-containing glycerol was added to a final concentration of2×YET/3% glycerol. Approximately 24 hr later, cells were harvested,washed, and stored at −70° C.

Human Phosphodiesterase Preparations

Phosphodiesterase Activity Determinations

Phosphodiesterase activity of the preparations was determined asfollows. PDE assays utilizing a charcoal separation technique wereperformed essentially as described in Loughney et al. (1996). In thisassay, PDE activity converts [32P]cAMP or [32P]cGMP to the corresponding[32P]5′-AMP or [32P]5′-GMP in proportion to the amount of PDE activitypresent. The [32P]5′-AMP or [32P]5′-GMP then was quantitativelyconverted to free [32P]phosphate and unlabeled adenosine or guanosine bythe action of snake venom 5′-nucleotidase. Hence, the amount of[32P]phosphate liberated is proportional to enzyme activity. The assaywas performed at 30° C. in a 100 μL reaction mixture containing (finalconcentrations) 40 mM Tris HCl (pH 8.0), 1 μM ZnSO₄, 5 mM MgCl₂, and 0.1mg/mL bovine serum albumin (BSA). PDE enzyme was present in quantitiesthat yield <30% total hydrolysis of substrate (linear assay conditions).The assay was initiated by addition of substrate (1 mM [32P]cAMP orcGMP), and the mixture was incubated for 12 minutes. Seventy-five (75)μg of Crotalus atrox venom then was added, and the incubation wascontinued for 3 minutes (15 minutes total). The reaction was stopped byaddition of 200 μL of activated charcoal (25 mg/mL suspension in 0.1 MNaH₂PO₄, pH 4). After centrifugation (750×g for 3 minutes) to sedimentthe charcoal, a sample of the supernatant was taken for radioactivitydetermination in a scintillation counter and the PDE activity wascalculated.

Purification of PDE5 from S. cerevisiae

Cell pellets (29 g) were thawed on ice with an equal volume of LysisBuffer (25 mM Tris HCl, pH 8, 5 mM MgCl₂, 0.25 mM DTT, 1 mM benzamidine,and 10 μM ZnSO₄). Cells were lysed in a Microfluidizer® (MicrofluidicsCorp.) using nitrogen at 20,000 psi. The lysate was centrifuged andfiltered through 0.45 μm disposable filters. The filtrate was applied toa 150 mL column of Q SEPHAROSE® Fast-Flow (Pharmacia). The column waswashed with 1.5 volumes of Buffer A (20 mM Bis-Tris Propane, pH 6.8, 1mM MgCl₂, 0.25 mM DTT, 10 μM ZnSO₄) and eluted with a step gradient of125 mM NaCl in Buffer A followed by a linear gradient of 125-1000 mMNaCl in Buffer A. Active fractions from the linear gradient were appliedto a 180 mL hydroxyapatite column in Buffer B (20 mM Bis-Tris Propane(pH 6.8), 1 mM MgCl₂, 0.25 mM DTT, 10 μM ZnSO₄, and 250 mM KCl). Afterloading, the column was washed with 2 volumes of Buffer B and elutedwith a linear gradient of 0-125 mM potassium phosphate in Buffer B.Active fractions were pooled, precipitated with 60% ammonium sulfate,and resuspended in Buffer C (20 mM Bis-Tris Propane, pH 6.8, 125 mMNaCl, 0.5 mM DTT, and 10 μM ZnSO₄). The pool was applied to a 140 mLcolumn of SEPHACRYL® S-300 HR and eluted with Buffer C. Active fractionswere diluted to 50% glycerol and stored at −20° C.

The resultant preparations were about 85% pure by SDS-PAGE. Thesepreparations had specific activities of about 3 μmol CGMP hydrolyzed perminute per milligram protein.

Inhibitory Effect on cGMP-PDE

cGMP-PDE activity of compounds of the present invention was measuredusing a one-step assay adapted from Wells et al., Biochim. Biophys.Acta, 384, 430 (1975). The reaction medium contained 50 mM Tris-HCl, pH7.5, 5 mM magnesium acetate, 250 μg/ml 5′-Nucleotidase, 1 mM EGTA, and0.15 μM 8-[H³]-cGMP. Unless otherwise indicated, the enzyme used was ahuman recombinant PDE5 (ICOS Corp., Bothell, Wash.).

Compounds of the invention were dissolved in DMSO finally present at 2%in the assay. The incubation time was 30 minutes during which the totalsubstrate conversion did not exceed 30%.

The IC₅₀ values for the compounds examined were determined fromconcentration-response curves typically using concentrations rangingfrom 10 nM to 10 μM. Tests against other PDE enzymes using standardmethodology showed that compounds of the invention are selective for thecGMP-specific PDE enzyme.

Biological Data

The compounds according to the present invention were typically found toexhibit an IC₅₀ value of less than 500 nM (i.e., 0.5 μM). In vitro testdata for representative compounds of the invention is given in thefollowing table:

TABLE 1 In vitro Results Example PDE5 IC₅₀ (μM) 1  0.0014 2  0.0075 3 0.0025 4  0.0018 7  0.0062 8  0.13 9  0.07 (Bov. aorta)¹⁾ 10  0.005(Bov. aorta) 11  0.65 (Bov. aorta) 12  0.1 (Bov. aorta) 13  0.25 (Bov.aorta) 14  0.08 (Bov. aorta) 15  0.06 (Bov. aorta) 16  0.01(stereoisomer of Ex. 15) 17  0.01 18  0.04 19  0.004 (Bov. aorta) 20 0.01 (Bov. aorta) 21  0.16 (Bov. aorta) 22  0.47  1.61 (Bov. aorta) 23 0.12  0.41 (Bov. aorta) 24  0.0096 25  0.01 26  0.01 27  0.0054 28 0.0039 29  0.0059 30  0.02 31  0.02 32  0.01 33  0.01 34  0.01 35 0.0043 36  0.05 37  0.03 38  0.0039 39  0.03 40  0.01 41  0.02 42  0.1443  0.1 44  0.4 45  0.08 46  0.05 47  0.0043 48  0.02 49  0.07 50 52.1(Bov. aorta) 51  0.0059 (stereoisomer of Ex. 50) 52  0.01 53  0.55 54 0.09 55  0.05 56  0.0042 57  0.0051 58  0.02 59  0.07 60  0.01 61  0.0162  0.02 63  0.13 64  0.02 65  0.63 66  0.04 67  0.0062 68  0.04 69 0.02 70  0.0084 71  0.01 72  0.0023 73  0.09 75  0.05 76  0.0088 77 0.0017 78  0.1 79  0.0063 80  0.07 81  0.29 82  0.03 83  0.04 84  0.1285  0.02 86  0.07 87  0.02 88  0.11 ¹⁾IC₅₀ determination made using PDE5obtained from bovine aorta.

Obviously, many modifications and variations of the invention ashereinbefore set forth can be made without departing from the spirit andscope thereof, and, therefore, only such limitations should be imposedas are indicated by the appended claims.

1. A compound selected from the group consisting of4-[2-((6R,12aR)-6-benzo[1,3]dioxol-5-yl--1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino-[1′,2′:1,6]-pyrido[3,4-b]indol-2-yl)ethyl]-benzenesulfonamide;(6R,12aR)-6-benzo[1,3]dioxo-5-yl-2-hydroxy-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-methoxy-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-2-amino-6-benzo[1,3]dioxo-5-yl-1,2,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-methylamino-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]-pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-phenyl-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(2-dimethylaminoethyl)-3-methyl-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(+−,cis)-2-(2-dimethylamino-ethyl)-6-(4-methoxy-phenyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(+−,cis)-6-benzo[1,3]dioxol-5-yl-2-(2-hydroxyethyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(+−,cis)-2-(3-dimethylaminopropyl)-6-(4-methoxyphenyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(+−,cis)-6-(4-methoxyphenyl)-2-[3-(4-methylpiperazin-1-yl)propyl]-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(+−,cis)-6-benzo[1,3]dioxol-5-yl-2-(2-piperidin-1-ylethyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(+−,cis)-6-benzo[1,3]dioxol-5-yl-2-(-2-diethylaminoethyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(+−,cis)-6-benzo[1,3]dioxol-5-yl-2-(2-morpholin-4-ylethyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(2-morpholin-4-ylethyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-(4-methoxyphenyl)-2-(2-morpholin-4-ylethyl)-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(3-morpholin-4-ylpropyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(+−,cis)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino-[1′,2′:1,6]pyrido-[3,4-b]indole-2-yl)aceticacid methyl ester;2-((+−,cis)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]pyrido[3,4-b]indol-2-yl)-acetamide;(+−,cis)-2-(1-azabicyclo[2.2.2]oct-3-yl)-6-benzo[1,3]dioxol-5-yl-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(+−,cis)-6-benzo[1,3]dioxol-5-yl-2-(2-diisopropylaminoethyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(+−,cis)-2-(1-azabicyclo[2.2.2]oct-3-yl)-6-benzo[1,3]dioxol-5-yl-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;3-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indol-2-yl)propionicacid ethyl ester;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(3-methoxypropyl)-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]-pyrido[3,4-b]indole-1,4-dione;N-[2-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indol-2-yl)-ethyl]-acetamide;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-[3-(2-oxopyrrolidin-1-yl)propyl]-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;2-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indol-2-yl)-N-phenylacetamide;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(2-methoxyethyl)-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]-pyrido[3,4-b]indole-1,4-dione;2-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indol-2-yl)-N-benzylacetamide;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(2-oxo-2-piperidin-1-ylethyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(3-imidazol-1-ylpropyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;3-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indol-2-yl)-N-cyclohexylpropionamide;3-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-indol-2-yl)-N-butyl-N-methylpropionamide;4-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indol-2-yl)-N-cyclohexylbutyramide;3-((6R,12aS)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indol-2-yl)propionicacid;(+−,cis)-6-benzo[1,3]dioxol-5-yl-2-(tetrahydrofuran-2-ylmethyl)-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;2-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indol-2-yl)-N-pyridin-4-ylacetamide;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(3-ethoxypropyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-[2-(2-hydroxyethoxy)ethyl]-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-((R)-2-hydroxypropyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-[2-oxo-2-(4-phenylpiperazin-1-yl)ethyl]-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;2-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indol-2-yl)-N-methyl-N-phenylacetamide;(+−,cis)-2-[2-(3-azabicyclo[3.2.2]non-3-yl)-ethyl]-6-benzo[1,3]dioxol-5-yl-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aS)-6-benzo[1,3]dioxol-5-yl-2-(1H-benzoimidazol-2-ylmethyl)-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-[2-(4-methylpiperazin-1-yl)ethyl]-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;4-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-1H-pyrazino[1′,2′:1,6]pyrido[3,4-b]indole-2-ylmethyl)benzoicacid;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(4-dimethylaminobenzyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(4-dimethylaminobenzyl)-3-methyl-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(+−,trans)-6-benzo[1,3]dioxol-5-yl-2-[2-((2R,6S)-2,6-dimethylmorpholin-4-yl)ethyl]-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(+−,cis)-6-benzo[1,3]dioxol-5-yl-2-[2-((2S,6R)-2,6-dimethylmorpholin-4-yl)ethyl]-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-2-[2-((2S,6R)-2,6-dimethyl-morpholin-4-yl)ethyl]-6-(4-methoxyphenyl)-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(2-imidazol-1-ylethyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-[2-(2-methylimidazol-1-yl)ethyl]-2,3,6,7,12,12a-hexahydropyrazino[1′,21:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(2-imidazol-1-ylethyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-2-(4-aminobenzyl)-6-benzo[1,3]-dioxol-5-yl-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;N-[4-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-pyrazino[1′,2′:1,6]pyrido[3,4-b]indol-2-yl-methyl)phenyl]-1,1,1-trifluoromethanesulfonamide;4-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indol-2-ylmethyl)-benzenesulfonamide;4-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indol-2-ylmethyl)-benzonitrile;(6-benzo[1,3]dioxol-4-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indol-2-yl)acetonitrile;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(1H-benzoimidazol-2-ylmethyl)-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;3-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indol-2-ylmethyl)-benzoicacid methyl ester;(+−,cis)-6-benzo[1,3]dioxol-5-yl-2-[2-(1-methylpyrrolidin-2-yl)ethyl]-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-[2-(1H-imidazol-4-yl)ethyl]-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(4-dimethylaminomethylbenzyl)-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-2-[2-(4-aminophenyl)ethyl]-6-benzo[1,3]dioxol-5-yl-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]pyrido-[3,4-b]indol-2-yl)aceticacid benzyl ester;((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]pyrido-[3,4-b]indol-2-yl)aceticacid;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-[3-(3,5-dimethylpyrazol-1-yl)propyl]-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;3-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indol-2-yl)propionicacid tert-butyl ester;3-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indol-2-yl)propionicacid;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(3-dimethylaminomethylbenzyl)-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(2-pyrazol-1-ylethyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(3-nitrobenzyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-2-(3-aminobenzyl)-6-benzo[1,3]-dioxol-5-yl-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;N-[3-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indole-2-ylmethyl)phenyl]-1,1,1-trifluoromethanesulfonamide;(6R,12aR)-6-benzofuran-5-yl-2-(2-pyrazol-1-ylethyl)-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]-pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(3-pyrazol-1-ylpropyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(4-benzyloxybenzyl)-2,3,6,7,12,12a-hexahydropyrazino-[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-[4-(2-dimethylaminoethoxy)benzyl]-2,3,6,7,12,12a-hexahydropyrazino[1,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(2-[1,4,5]triazol-1-ylethyl)-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(4-methylamino-3-nitrobenzyl)-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;2-((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]-pyrido[3,4-b]indol-2-yl)-N-(4-methyl-piperazin-1-yl)acetamide;(6R,12aR)-6-benzo[1,3]dioxol-5-yl-2-(1-methyl-1H-benzoimidazol-5-ylmethyl)-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione;((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]pyrido-[3,4-b]indol-2-yl)aceticacid tert-butyl ester;((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]pyrido-[3,4-b]indol-2-yl)aceticacid methyl ester;((6R,12aR)-6-benzo[1,3]dioxol-5-yl-1,4-dioxo-3,4,6,7,12,12a-hexahydro-1H-pyrazino[1′,2′:1,6]pyrido-[3,4-b]indol-2-yl)aceticacid octyl ester; and pharmaceutically acceptable salts and solvatesthereof.